Why cancer screening has never been shown to “save lives”—and what we can do about it
BMJ 2016; 352 doi: https://doi.org/10.1136/bmj.h6080 (Published 06 January 2016) Cite this as: BMJ 2016;352:h6080Including all mortality
Click here to see an infographic, explaining why reporting all causes of mortality in cancer screening trials is so important.
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Cervical screening does reduce mortality.
These authors are right to point out that most cancer screening has not been shown to save lives, because single trials to prove reduction in total mortality from screening for any one cancer at a time would be too large to be practicable. So decisions have to be made on the best available evidence. Part of the problem is that evidence that was good enough in the past is now regarded by purists as methodologically inadequate. But that does not mean that we should discard it. Simply because a proposition has not been demonstrated with a randomised trial does not mean it is wrong. RCTs are necessary when the evidence is equivocal, not when it is overwhelming. No trials were performed to show that smoking caused lung cancer and other diseases, and no one would seriously suggest one. In the field of cancer, cervical screening is the best example.
This cancer that used to kill over 1% of women is now rare in countries that screen consistently. Because this cancer affects young to middle-aged women, for whom there are few other competing causes of death, and the size of the incidence and mortality reduction is so great, its value was demonstrated in the 1970s to 1980s with a series of ecological studies, comparing regions or countries that introduced screening at different time periods, and case control studies1. The consistency of these different types of studies and the current differences between countries that screen and those that do not is so great that it is difficult to ascribe any other cause but screening2,3.
Biologically, cervical screening works because it detects and permits treatment of pre-cancers and very early invasive cancers – admittedly at the price of substantial overdiagnosis and overtreatment, which should be minimised in an effective program. The authors are right to point out that screening is less effective for the other cancers they discuss: in part because they detect disease at a later stage and at later ages. Cervical screening is an exception to their general rule.
1. Miller AB, Lindsay J, Hill GB. Mortality from cancer of the uterus in Canada and its relationship to screening for cancer of the cervix. Int J Cancer 1976: 17, 602-612.
2. IARC Working Group on the Evaluation of Cancer-Preventive Strategies. Cervix cancer screening. IARC 2004: Lyon, France
(IARC Handbooks of Cancer Prevention; 10)
3. Arbyn M, Raifu AO, Autier P, Ferlay J. Burden of Cervical Cancer in Europe: estimates for 2004. Annals of Oncology 2007: 18, 1708-1715,
Competing interests: I was the lead author for the Canadian Task Force on Preventive Health Care recommendations on Cervical Screening.
Declining cancer screening is certainly not reasonable specifically in case of persons with high risk of oral cancer. Oral cancer is responsible for 8000 deaths annually in America and 5 year survival rate is only 30% [1]. This high rate of mortality is due to non-detection of oral cancer at initial stages. However if it is detected in the initial stages the overall survival rate is 90% [1]. Hence oral cancer screening especially in high risk patients is a must. Doctors, dentists and nurses should be especially trained to identify initial precancerous lesions such as leukoplakia and erythroplakia. Physicians, dentists and nurses should include oral cavity examination in their routine clinical examination. Screening for oral cancer especially in the high risk patients who consume tobacco and alcohol certainly helps in reducing the overall mortality due to oral cancer and saves lives.
References
Competing interests: No competing interests
Many thanks to Andrew W. Swartz for pointing out an error in the infographic accompanying the article. I have corrected the text in the "study power" box, which now states that studying all-cause mortality requires a larger, rather than a smaller, sample size, than disease-specific outcomes.
Competing interests: No competing interests
If we really want to be honest, we should compare also the negative effects of screening with a control population.
As an example, do we find MORE psychosocial distress among those who received a positive screening test than what we wuld normally observe in a control population (same age, sex, etc), as we know that psychosocial distress is already quite high in an aging population.
Note: I am not a fervent advocate of screening when the quality of life is diminished, and it is always diminished for a certain period of time, whether it be in the waiting period of confirming or not the diagnosis, during the treatment, if necessary, with its secondary effects, or the recuperation time, when, by definition, those who undergo a screening test are not yet symptomatic and might never be.
Competing interests: No competing interests
If cancer screening has never been shown to “save lives” it could be because important causes of cancer have been ignored. Cervical screening was introduced because the increases in positive smears caused by increased infection and use of oral contraceptives in the 1960s. Breast cancer screening for middle aged women was a response the increases in breast cancer in the generations who took oral contraceptives followed by HRT. Several times the use of progestogens and oestrogens have fallen so has the incidence of breast cancer and breast cancer mortality in the affected age groups. Screening will not save lives if the underlying causes of cancers continue to be vigorously promoted.
www.harmfromhormones.co.uk
Competing interests: No competing interests
This is a very useful article and should be widely read, but I want to draw attention to the ethics of always necessarily sacrificing some lives in order to preserve others.
My comment here explores the ethics of screening and predictive diagnostics from a (up til now) neglected biopolitical perspective. It introduces an academic domain that up to now has had little inter-disciplinary overlap with Evidence Based Medicine. And although some of the language and concepts here may seem a little esoteric I would ask you to persevere. This concerns the domain of Biopolitics. Biopolitics explores the relation, and the effects of this relation, between the political order (ideologies if you like, increasingly neoliberal today) and Bíos, a term used by Esposito to describe a biological life conforming to and objectvised by the political order (Esposito, 2008a, b).
Medical screening to measure the risks of, and to prevent, future ill health is an example of what the Italian philosopher Esposito, in his book Bíos, has identified as an immunitary mechanism that functions, ostensibly, in the name of 'preserving life'. (Esposito 2008a) However this function, Esposito claims, is only secondary to its primary function, which is to act as a kind of biopolitical glue binding together and maintaining and reproducing the political order (today - neoliberalism) with a biological life of a subject (bíos) that is subjugated to and is an object for this political order. Biological Life's innate instability over time and neoliberalism's demand for economic growth lead to an ongoing intensification of these mechanisms. The paper by Prasda et al (Prasad, Lenzer, and Newman, 2016) is a very useful demonstration of the coincident sacrifice and destruction of life that can only increase as the immunitary mechanisms intensify. Esposito might claim (on the basis of his writings in Bíos) that only the development of a new ethical relationship to life itself by the medical profession and patients, that begins to refuses the sacrifice of one life for another, will slow this process down. In addition a fundamental break with neoliberalism’s influence on medical practice would also address the impact of politics on so-called patients' 'values'- values not at present generated by the individual but constituted by a subject subjugated by the political order.
As in this paper by Prasad et al(Prasad et al., 2016) the resistance to such destructive mechanisms focuses mostly on regulation, bigger studies, 'more honesty' and shared decision making (SDM). But we can see that these, alone, can and will never succeed in preventing an increasingly destructive (even thanatopolitical) process. These strategies may even function, given biopolitical politico-economic imperatives and power, to legitimate further intensifications in the longer run.
These resistive measures do not address the biopolitical and therefore the structurally neccessary 'tremendous prophylactic' (Nietzsche 1986) p113 immunitary drivers that maintains the subjugation of the population necessarily and reciprocally bound to and maintaining the existing social order and its socio-economic inequalities.
“….. against the vacuum of sense that opens at the heart of life that is ecstatically full of itself, the general process of immunization is triggered…. ‘the democratization of Europe is, it seems, a link in the chain of those tremendous prophylactic measures which are the conceptions of modern times.’” (Esposito, 2008a) p89, cites (Nietzsche, 1986) p113
Yes, medical practice, sometimes ethically, prevents suffering more or less in two ways a) the suffering today and b) preventing suffering tomorrow. But is it always ethical if it involves sacrificing one life for another, and when an individual does not know whether his body is being preserved or sacrificed or even both. Resistance to the excess of destruction is an important but biopolitical struggle. However the efforts by those resisting screenings excesses focus on a struggle that is not seen for what it is. On the surface are the effects of systems using forms of biological knowledge in a struggle between a) interventions for profit and power, and b) non-intervention, sacrificing power and profit. But this is secondary to the primary biopolitical struggle: between a) preserving an anticipated future life by eradicating risk, versus b) allowing a life today to take its chances and face risk, or if you like between preserving by sacrificing life or nor preserving life. Preventive screening and predictive medical interventions can either preserve life now or life in the future but either way must entail more or less sacrifice, destruction and weakening of life. New questions, language and strategies for medicine can emerges from Esposito's writings such: Is the intervention necessary? is it always ethical to weaken one life in order to strengthen another? Is it ethical to divide lives ‘worth living’ from ‘lives not worth living’ on economic grounds?
The French doctor and philosopher (and French resistance activist fighting the Nazis) Canguilhem introduced the idea of normative man, and life itself as its own norm, not a panacea in itself but worth consideration:
“health is in no way a demand of the economic order that is to be weighed when legislating, but rather is the spontaneous unity of the conditions for the exercise of life.” (Esposito, 2008a) p189 citing Canguilhem ‘Une pédagogie de la guérison est-elle possible?’ In ‘Écrits sur la medicine’ (Paris editions, du Seuil, 2002, p89)
Esposito, R. (2008a) Bios: Biopolitics and Philosophy. Minneapoli: University of Minnesota.
Esposito, R. (2008b) The Immunization Paradigm. diacritics, 36(2): 23-48.
Nietzsche, F.W. (1986) Human, All Too Human. A Book For Free Spirits. Cambridge: Cambridge University Press.
Prasad, V., Lenzer, J., & Newman, D. (2016) Why cancer screening has never been shown to “save lives”—and what we can do about it. BMJ, 352.
Competing interests: No competing interests
Thank you Dr Prasad, Ms Lenzer and Dr Newman on an excellent article and for driving the paradigm of medicine towards empirical evidence over proposed mechanisms. Thank you for challenging conventional wisdom and forcing us to ask, "What are the truly important patient centered outcomes".
If we cannot change "conventional wisdom" with evidence then we are truly no different than the in doctors in Colonial America who believed that drawing blood could accelerate coagulation. They too had examples of their technique working and a robust explanation of why it was unethical to challenge their practice. It takes great courage to speak out and to go against the grain.
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The Infographic contains an error. The box labelled "Study power" incorrectly states that "Studying disease-specific outcomes requires a much LARGER sample size than all-cause mortality." The correct statement is that it requires a SMALLER sample size.
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We are deeply concerned that these authors are drawing broad, sweeping conclusions about the value of screening from a narrow set of data. Contrary to what this paper suggests, numerous scientific studies have clearly and conclusively demonstrated that screening reduces mortality and morbidity for a large number of diseases and conditions, including cancer. Ensuring appropriate access to critical screening procedures enables earlier detection and diagnosis, when the disease is typically easier and less costly to treat. While our collective understanding of the value of these procedures will undoubtedly evolve as new research becomes available, it is imperative that we encourage patients to seek appropriate screening tests, rather than deterring them with misleading, ill-founded headlines.
Competing interests: No competing interests
Re: Why cancer screening has never been shown to “save lives”—and what we can do about it
A useful companion to this highly informative paper is the recent short communication by Welch et al (Trends in metastatic breast and prostate cancer--Lessons in cancer dynamics, NEJM 373,1685-7, 2015), who in less than three pages and a single figure effectively demolish the value of any screening program based on current paradigms of screening.
Competing interests: No competing interests